A quantum mechanically study of silicon nanograins with an aluminum overlayer: structural properties and electronic charge

The purpose of this study is the evaluation of the effects of a metallic overlayer on nanocrystalline silicon grains and is based on the Hartree-Fock formulation at semiempirical level and on the Density Functional theory. The structures considered are crystalline grains with a spherical, columnar or T-shaped structure. The ones with mixed composition are constructed by depositing an aluminum layer on the grains with the plated form. The calculations indicate that the aluminum atoms retain the layered distribution without clustering, which is also a property of the bulk samples. The evaluation of the Fermi level suggests the formation of a Schottky barrier and the features of the states localized at the interface indicates quantum confinement. Both properties would be of interest for electronic devices at the nanoscale. However the strength of bonding is generally lower in the structures with contacts and this casts doubts on the stability of structures of this mixed type.